1. Field of the Invention:
This invention relates to a device for precisely positioning a workpiece relative to a tool which is to work on the workpiece. More particularly, this invention relates to a device for precisely positioning a printed circuit board relative to a solderer/desolderer for the attachment or removal of modular electronic components.
2. Description of the Prior Art
Present day devices for removing or installing modular electronic components from a substrate such as a printed circuit board generally fall into two categories: those which use a heated head which contacts each terminal to melt the solder thereon or those which use a blast of hot air to melt the solder. The former devices are generally very complex and employ a heated head having a plurality of spaced apart fingers each of which must be precisely aligned with each terminal around the component to simultaneously heat the solder on it. The component is then withdrawn from the substrate by vacuum suction or other mechanical means. The procedure is reversed for installing a component. An example of such a device is disclosed in U.S. Pat. No. 3,382,564. A major disadvantage of this type of device is that, due to the ever-increasing minaturization of electronic systems and individual components in them, the terminals of such components are extremely close together thus making precise alignment of the fingers of the heating head therewith extremely difficult. Improper alignment or contact often results in solder flowing between terminals on the component thus shorting them or otherwise damaging them. The latter devices direct a blast of hot air at the terminals from a source above the component to simultaneously melt the solder on each. Such a device, for example, is set forth in U.S. Pat. No. 4,366,925. Such a device may function satisfactorily if there is a large spacing between components such that the blast of hot air directed at one component from above will not spill over and melt the solder on the terminals of adjacent components. However, as aforementioned, not only are the components themselves becoming increasingly smaller but their proximity on the printed circuit substrate is also increasing. A device which cannot only provide a closely controlled and evenly distributed source of heat sufficient to melt solder associated with component terminals or printed substrate conductors during installation or removal of the electronic component relative thereto but one which can rapidly and precisely direct this controlled heat where desired thereby minimizing the likelihood of melting the solder on the terminals of adjacent components or otherwise damaging the printed conductors on the substrate is disclosed in commonly assigned, copending application Ser. No. 649,065, filed Sept. 10, 1984. However, this device for heating the solder associated with component terminals utilizes a precisely directed flow of hot air toward each component terminal or printed conductor on the substrate, which emphasizes the need to precisely position the nozzles from which the hot air is directed in relation to the component on the substate which is to be removed or attached. Thus, there is a need for a device which has the capability of precisely positioning the electronic component and its terminals on the ends of the printed conductors on the substrate to insure no overlapping, during placement or removal, or that no liquid solder is smeared on the substrate between the conductors printed thereon.